The invention relates generally to valves for controlling the flow of fluids, and more particularly, relates to a disposable manifold for directing the flow of blood wherein a rotatable valve controls flow through the manifold.
A substantial volume of blood is shed during many major surgical procedures, such as heart by-pass surgery and hip replacement surgery. Often the shed blood, which has been contaminated, is discarded and replaced with donor blood. Recently, an alternative procedure has been developed in which the shed blood is recovered, the contaminants removed, and the "uncontaminated" blood cells reinfused into the patient.
In this procedure, the fluid in the surgical site is collected using suction and is drawn into an evacuated reservoir. The fluid collected in the reservoir, called "shed blood", contains whole blood, saline used to rinse the surgical site, blood clots, bone chips, fatty tissue and other miscellaneous contaminants.
The collected shed blood may be disposed of in at least three ways. First, it may be discarded and the lost blood volume replaced by donor blood.
A second alternative is to filter the shed blood and transfuse it to the patient. The filter removes blood clots, bone chips and tissue from the shed blood, but the filtered shed blood remains diluted with the saline originally used to rinse the surgical site.
The third alternative is to "wash" the shed blood, as well as filter it. One way of washing shed blood is to use a centrifugal wash system. (See "The Preparation of Leukocyte-Poor Red Blood Cells: A Comparative Study, Meryman et al., Transfusion 20(3): 285: 287, 1980.) In a typical centrifugal wash system, shed blood is centrifuged while washing it with saline in a disposable centrifuge bowl or rotor. A typical bowl for such a system is the so-called Latham bowl, shown in U.S. Pat. No. 4,300,717. Since red cells have a higher density than saline or blood plasma, the red cells fill the outermost portion of the rotating centrifuge bowl. As more shed blood enters the bowl, the red cells remain in the bowl displacing the supernatant (saline, plasma, contaminants, etc.) out of the bowl. This concentrates the red blood cells in the bowl. Next, saline is directed into the bowl, instead of shed blood. Saline, entering the bowl, is directed by the lower extended skirt portion of the core to the outermost radius of the bowl and through the bed of packed red blood cells. In this way, the supernatant is diluted and displaced by the saline until a satisfactory "washout" efficiency is obtained.
In the processing of shed blood, it is necessary to interconnect numerous devices and fluid reservoirs along sterile closed fluid pathways. Often this is done with flexible tubing wherein pneumatic, manual, or electrically actuated clamps or manual slide clamps are used to individually open or close various sections of tubing to control the fluid flow.
During the processing of the blood, the operator must manually open or close the clamps corresponding to the desired operation. This operator-dependent system can result in errors such as placing the tubing in the wrong clamps or operating the wrong clamp at an improper time. Additional time is required for operator training to insure efficient and safe use.
Many valve mechanisms that control fluid flow depend upon rotation of an inner member that defines a fluid pathway within an outer member. The relative position of the two members determines whether the fluid path is open or closed. A glass stopcock is one example of such a valve which utilizes a rotating seal such as an O-ring to prevent leakage. Such a seal is complex and in the present application presents problems of biocompatibility between the valve material and the blood.